NRAMP1 gene polymorphisms in patients with rheumatoid arthritis in Koreans

Human Genetic Variation Influences Enteric Fever Progression

In the 21st century, enteric fever is still causing a significant number of mortalities, especially in high-risk regions of the world. Genetic studies involving the genome and transcriptome have revealed a broad set of candidate genetic polymorphisms associated with susceptibility to and the severity of enteric fever. This review attempted to explain and discuss the past and the most recent findings on human genetic variants affecting the progression of Salmonella typhoidal species infection, particularly toll-like receptor (TLR) 4, TLR5, interleukin (IL-) 4, natural resistance-associated macrophage protein 1 (NRAMP1), VAC14, PARK2/PACRG, cystic fibrosis transmembrane conductance regulator (CFTR), major-histocompatibility-complex (MHC) class II and class III. These polymorphisms on disease susceptibility or progression in patients could be related to multiple mechanisms in eliminating both intracellular and extracellular Salmonella typhoidal species. Here, we also highlighted the limitations in the studies reported, which led to inconclusive results in association studies. Nevertheless, the knowledge obtained through this review may shed some light on the development of risk prediction tools, novel therapies as well as strategies towards developing a personalised typhoid vaccine.

Role of Infections in the Pathogenesis of Rheumatoid Arthritis: Focus on Mycobacteria

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease characterized by chronic erosive polyarthritis. A complex interaction between a favorable genetic background, and the presence of a specific immune response against a broad-spectrum of environmental factors seems to play a role in determining susceptibility to RA. Among different pathogens, mycobacteria (including Mycobacterium avium subspecies paratuberculosis, MAP), and Epstein–Barr virus (EBV), have extensively been proposed to promote specific cellular and humoral response in susceptible individuals, by activating pathways linked to RA development. In this review, we discuss the available experimental and clinical evidence on the interplay between mycobacterial and EBV infections, and the development of the immune dysregulation in RA.

Correlation of Polymorphisms of Natural Resistance-Associated Macrophage Protein 1 (NRAMP1) Gene and Smoking with the Risk of Rheumatoid Arthritis in Chinese Han People

Background

In this study we report on the possible connection between single nucleotide polymorphisms (SNPs) in natural resistance-associated macrophage protein 1 (NRAMP1) gene and the risk of rheumatoid arthritis (RA) in the Chinese Han population.

Material/Methods

A total of 248 participants consisting of 116 RA cases and 132 healthy individuals were recruited for the current study. Genotyping for NRAMP1 gene polymorphisms was implemented using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The chi-square test was used to detect discrepancies in genotype and allele frequencies between the RA case group and the control group. Odds ratios (ORs) with 95% confidence intervals (CIs) was used to evaluate relative risk of RA. The results were adjusted by logistic regression analysis.

Results

The TT genotype and T allele in rs17221959 showed dramatically different distribution between RA cases and healthy controls. After adjustment, TT genotype (OR=0.338, 95%CI=0.278–1.214, P=0.028) and T allele (OR=0.608, 95%CI=0.298–0.956, P=0.005) showed close association with reduced risk of RA. For rs1059823, no obvious diversity was uncovered in either genotype or allele distribution between the 2 groups. Interaction analysis showed that smoking decreased the protective function of TT in rs17221959.

Conclusions

This study suggested that the TT genotype and T allele in rs17221959 decreased RA risk. Smoking could decrease the protective effect of TT.

Association between rheumatoid arthritis and genetic variants of natural resistance-associated macrophage protein 1 gene: A meta-analysis

AIM

To evaluate the association between natural resistance-associated macrophage protein 1 (NRAMP1) polymorphisms and rheumatoid arthritis (RA).

METHOD

All related studies were retrieved and screened from PubMed, CNKI and Web of Science. Pooled odds ratios (ORs) and 95% CIs were assessed for the strength of association between NRAMP1 and RA. Publication bias was measured by Begg's funnel plot and Egger's regression test. The robustness of this meta-analysis was detected by sensitivity analysis.

RESULTS

A total of five eligible publications were included in the present meta-analysis. The polled data showed no association between RA and NRAMP1 D543N and 1729 + 55del4 in the allele model. However, the relationship between RA and NRAMP1 INT4 was statistically significant (OR 1.65, 95% CI 1.14-2.38). Genotypic analysis demonstrated that there were no associations between RA and NRAMP1 D543N, 1729 + 55del4 and INT4 in homozygous comparison (D543N: OR 0.97, 95% CI 0.15-6.09; 1729 + 55del4: OR 1.19, 95% CI 0.29-24.88; INT4: OR 3.18, 95% CI 0.62-16.26), dominant model (D543N: OR 1.04, 95% CI 0.61-61.78; 1729 + 55del4: OR 1.41, 95% CI 0.81-2.47; INT4: OR 1.22, 95% CI 0.72-2.06) and recessive model (D543N: OR 0.93, 95% CI 0.15-5.91; 1729 + 55del4: OR 0.99, 95% CI 0.26-3.86; INT4: OR 2.95, 95% CI 0.61-14.16). In heterozygous comparison, it no association was shown between RA and NRAMP1 D543N and INT4, excepting NRAMP1 1729 + 55del4 (OR 1.73, 95% CI 1.17-2.56). Further subgroup analysis indicated that NRAMP1 1729 + 55del4 and INT4 were related to RA in Asia and in the Hardy-Weinberg equilibrium group. There exists no publication bias in this meta-analysis.

CONCLUSION

This meta-analysis indicated that NRAMP1 1729 + 55del4 and INT4 confer susceptibility to RA.

Mycobacterium avium subspecies paratuberculosis: A possible causative agent in human morbidity and risk to public health safety

Mycobacterium avium subspecies paratuberculosis is a bacterial parasite and the causative agent of paratuberculosis, a disease predominately found in cattle and sheep. Infection with this microorganism results in substantial farming economic losses and animal morbidity. The link between infection with this pathogen and human disease has been theorised for many years with Crohn's disease being one of many suspected resultant conditions. Mycobacterium avium may be spread from animal to human hosts by water and foodborne transmission routes, where the foodborne route of exposure represents a significant risk for susceptible populations, namely children and the immune-compromised. Following colonisation of the host, the parasitic organism evades the host immune system by use of molecular mimicry, displaying peptide sequences similar to that of the host cells causing a disruption of self-verses non self-recognition. Theoretically, this failure to recognise the invading organism as distinct from host cells may result in numerous autoimmune conditions. Here, the author presents current information assessing the link between numerous diseases states in humans such inflammatory bowel disease, Type 1 diabetes, rheumatoid arthritis, Hashimoto\'s thyroiditis, multiple sclerosis and autism following infection with Mycobacterium avium paratuberculosis. The possibility of zoonotic transmission of the organism and its significant risk to public health safety as a consequence is also discussed.

NRAMP1 Polymorphisms like Susceptibility Marker in Mexican Focus of Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) is endemic in Campeche state, Mexico. Host and parasite factors are involved in the establishment and development of CL. Host factors include immune response and genetic background. NRAMP1 (Natural Resistance Associated Macrophage Protein 1) is important in innate immunity. Polymorphisms in NRAMP1 have been associated with susceptibility or resistance to infectious and autoimmune diseases. To study the association of NRAMP1 mutations with CL in patients from Calakmul, Campeche, samples from 115 CL patients and 69 samples of healthy people from the same area were evaluated. Five regions in NRAMP1 were amplified and digested, looking for mutations in the promoter region (−524G/C), exon 3 (274C/T), exon 8 (823 C7T), and exon 15 (G/A) and deletion of 4 bp in the 3′UTR region. We found a statistical association between polymorphisms in 3′UTR region and exon 8 and CL [χ² = 13.26; p < 0.05; OR = 17.00; IC of 95% (2.24–128.99)]. Some patients who needed more than 40 doses of Glucantime® to heal injuries presented mutations in exons 3, 8, and 15. Multiple or ear lesions were not associated with NRAMP1 polymorphism.

Transcription factor ATF-3 regulates allele variation phenotypes of the human SLC11A1 gene

Genetic polymorphisms in the human solute carrier family 11 member 1 (SLC11A1) gene predispose to susceptibility to infectious/inflammatory diseases and cancer. Human susceptibility to these diseases exhibits allelic association with a polymorphic regulatory Z-DNA-forming microsatellite of a (GT/AC)n repeat. The carriage of different alleles may influence chromatin remodeling and accessibility by transcription factors. Of particular importance is the binding site for the Activating Protein 1 (AP-1) elements, (ATF-3 and c-Jun), adjacent to the 5' sequence of the Z-DNA-forming polymorphism. The aim of the study was to characterize the transcriptional mechanisms controlling different alleles of SLC11A1 expression by ATF-3 and c-Jun. Allele 2, [T(GT)5AC(GT)5AC(GT)10GGCAGA(G)6], and Allele 3, [T(GT)5AC(GT)5AC(GT)9GGCAGA(G)6], were subcloned into the PGL2Basic vector. Transient transfections of THP-1 cells with the constructs, in the presence or absence of pATF-3 were preformed. Luciferase expression was determined. To document the recruitment of ATF-3 and c-Jun, to the polymorphic promoter alleles in vivo, we performed ChIP assays with transient transfected THP-1 cells treated with or without lipopolyssacharides. Our data documented that ATF-3 suppresses the transcriptional activation of Allele-3, and this suppression is enhanced in the presence of lipopolyssacharides. Our findings suggest that ATF-3 and c-Jun may influence heritable variation in SLC11A1-dependent innate resistance to infection and inflammation both within and between populations.

Evidence of association with type 1 diabetes in the SLC11A1 gene region

BACKGROUND

Linkage and congenic strain analyses using the nonobese diabetic (NOD) mouse as a model for human type 1 autoimmune diabetes (T1D) have identified several NOD mouse Idd (insulin dependent diabetes) loci, including Slc11a1 (formerly known as Nramp1). Genetic variants in the orthologous region encompassing SLC11A1 in human chromosome 2q35 have been reported to be associated with various immune-related diseases including T1D. Here, we have conducted association analysis of this candidate gene region, and then investigated potential correlations between the most T1D-associated variant and RNA expression of the SLC11A1 gene and its splice isoform.

METHODS

Nine SNPs (rs2276631, rs2279015, rs1809231, rs1059823, rs17235409 (D543N), rs17235416 (3'UTR), rs3731865 (INT4), rs7573065 (-237 C → T) and rs4674297) were genotyped using TaqMan genotyping assays and the polymorphic promoter microsatellite (GT)n was genotyped using PCR and fragment length analysis. A maximum of 8,863 T1D British cases and 10,841 British controls, all of white European descent, were used to test association using logistic regression. A maximum of 5,696 T1D families were also tested for association using the transmission/disequilibrium test (TDT). We considered P ≤ 0.005 as evidence of association given that we tested nine variants in total. Upon identification of the most T1D-associated variant, we investigated the correlation between its genotype and SLC11A1 expression overall or with splice isoform ratio using 42 PAXgene whole blood samples from healthy donors by quantitative PCR (qPCR).

RESULTS

Using the case-control collection, rs3731865 (INT4) was identified to be the variant most associated with T1D (P = 1.55 × 10-6). There was also some evidence of association at rs4674297 (P = 1.57 × 10-4). No evidence of disease association was obtained at any of the loci using the family collections (PTDT ≥ 0.13). We also did not observe a correlation between rs3731865 genotypes and SLC11A1 expression overall or with splice isoform expression.

CONCLUSION

We conclude that rs3731685 (INT4) in the SLC11A1 gene may be associated with T1D susceptibility in the European ancestry population studied. We did not observe a difference in SLC11A1 expression at the RNA level based on the genotypes of rs3731865 in whole blood samples. However, a potential correlation cannot be ruled out in purified cell subsets especially monocytes or macrophages.

Linking chronic infection and autoimmune diseases: Mycobacterium avium subspecies paratuberculosis, SLC11A1 polymorphisms and type-1 diabetes mellitus

BACKGROUND

The etiology of type 1 diabetes mellitus (T1DM) is still unknown; numerous studies are performed to unravel the environmental factors involved in triggering the disease. SLC11A1 is a membrane transporter that is expressed in late endosomes of antigen presenting cells involved in the immunopathogenic events leading to T1DM. Mycobacterium avium subsp. paratuberculosis (MAP) has been reported to be a possible trigger in the development of T1DM.

METHODOLOGY/PRINCIPAL FINDINGS

Fifty nine T1DM patients and 79 healthy controls were genotyped for 9 polymorphisms of SLC11A1 gene, and screened for the presence of MAP by PCR. Differences in genotype frequency were evaluated for both T1DM patients and controls. We found a polymorphism in the SLC11A1 gene (274C/T) associated to type 1 diabetic patients and not to controls. The presence of MAP DNA was also significantly associated with T1DM patients and not with controls.

CONCLUSIONS/SIGNIFICANCE

The 274C/T SCL11A1 polymorphism was found to be associated with T1DM as well as the presence of MAP DNA in blood. Since MAP persists within macrophages and it is also processed by dendritic cells, further studies are necessary to evaluate if mutant forms of SLC11A1 alter the processing or presentation of MAP antigens triggering thereby an autoimmune response in T1DM patients.

NRAMP1 (SLC11A1) gene polymorphisms that correlate with autoimmune versus infectious disease susceptibility in tuberculosis and rheumatoid arthritis

NRAMP1 gene has multiple pleiotropic effects on macrophage activation pathways. These pleiotropic effects may increase resistance to infections such as tuberculosis (TB), but may also lead to susceptibility of autoimmune diseases such as rheumatoid arthritis (RA). It has been hypothesized that allele 3 would be associated with autoimmune diseases, whereas allele 2 would be associated with infectious diseases, and genetic factors that enhanced survival in the epidemics of TB might have led to susceptibility for the development of RA. We analysed four NRAMP1 gene polymorphisms including 5' promoter (GT)(n) (rs34448891), INT4 (469 + 14G/C) (rs3731865), 3'UTR (1729 + 55del4) (rs17235416) and D543N (codon 543, Asp to Asn) (rs17235409) in 112 patients with TB, 98 patients with RA, 80 healthy controls for TB and 122 healthy controls for RA using ARMS-PCR and PCR-RFLP. We found a significant association between INT4 and RA (P = 0.004, odds ratio: 2.06, 95% CI: 1.24-3.41), but no significant differences between 5' promoter, D543N, 3'UTR polymorphisms and RA. There were no associations between NRAMP1 gene polymorphisms and TB. Similarly, no significant differences were observed between NRAMP1 polymorphisms and rheumatoid factor positivity and erosive disease in RA and localization of TB. INT4 polymorphism may be associated with RA in Turkish patients.

Role of functional polymorphisms of NRAMP1 gene for the development of Crohn's disease

BACKGROUND

Crohn's disease (CD) is characterized by chronic activation of macrophages. Natural resistance-associated macrophage protein 1 (NRAMP1) gene exerts many pleiotropic effects on macrophage functions. Hence, NRAMP1 may be also involved in the resistance to intracellular pathogens, and this effector of the innate immunity might be involved in CD pathogenesis. Polymorphic alleles at the NRAMP1 locus have been previously associated with susceptibility both to the putative infectious agents and to autoimmune disorders. Based on these indications, in the present study we investigate its candidacy as a genetic determinant for CD in a Greek population in an association-based study, comparing frequencies of 274 CD patients to these of 200 healthy control subjects.

METHODS

The 5'(GT)n promoter polymorphism and 9 either single nucleotide (SNPs) or insertion/deletion type polymorphisms were genotyped across the NRAMP1 gene. Reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry were performed in order to investigate the NRAMP1 mRNA levels in RNA isolated from biopsies of CD patients as well as protein expression in tissues.

RESULTS

Three NRAMP1 polymorphisms [5'(GT)n, D543N, and INT4G/C] were significantly associated with CD. Consistent with previous autoimmune disease studies, allele 3 at the functional 5'(GT)n promoter region repeat polymorphism, was significantly associated with CD when compared to healthy controls (odds ratio 1.50; 95% confidence interval [CI]: 1.16-1.95; P = 0.002). Interestingly, we observed that CD patients homozygous for allele 3 expressed higher NRAMP1 mRNA levels compared to carriers of allele 2. Furthermore, the protein levels of allele 3 carriers in tissues were also elevated compared to those of allele 2 carriers. Based on these data we can speculate that overrepresentation of allele 3 in CD patients could lead to hyperactivation of bowel-wall macrophages that are chronically exposed to lipopolysaccharide and this could subsequently cause the autoimmune-like phenotype characteristic of CD.

CONCLUSIONS

Collectively, our data indicate that genetic polymorphisms of NRAMP1 might be associated with susceptibility to CD.

SLC11A1 polymorphisms are associated with the risk of chronic obstructive pulmonary disease in a Korean population

The solute carrier family 11 member 1 (SLC11A1) protein plays important roles in macrophage activation and displays pleiotropic effects on various macrophage functions, including the regulation of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and oxidative burst. Considering the important roles of macrophage in the pathogenesis of chronic obstructive pulmonary disease (COPD), we hypothesized that the SLC11A1 gene may act as a low-penetrance susceptibility gene for COPD. To test this hypothesis, we first examined the frequencies of 12 candidate polymorphisms in the SLC11A1 gene in 27 healthy Korean individuals, and then genotyped 3 haplotype-tagging polymorphisms [IVS4 + 14G > C (rs3731865), D543 N (rs17235409), and (*)86A > G (rs1059823)] in 83 COPD patients and 203 healthy controls. Individuals with at least one variant allele of the D543 N and (*)86A > G polymorphisms were at a significantly increased risk for COPD compared with carriers with each homozygous wild-type allele [adjusted odds ratio (OR) = 2.23, 95% confidence interval (CI) = 1.24-4.02, P = 0.007; and adjusted OR = 1.92, 95% CI = 1.10-3.35, P = 0.022, respectively]. Consistent with the findings of the genotyping analysis, the 122 haplotype carrying both the 543 N and (*)86G alleles was associated with a significantly increased risk for COPD compared with the 111 haplotype with the 542D and (*)86A alleles (adjusted OR = 2.05, 95% CI = 1.19-3.51, P = 0.009 and Bonferroni corrected P = 0.027). These findings suggest that the SLC11A1 polymorphisms could be used as markers for genetic susceptibility to COPD. However, further studies with large numbers of subjects are needed to confirm our findings.

The human solute carrier family 11 member 1 protein (SLC11A1): linking infections, autoimmunity and cancer?

SLC11A1 is known to link infections, autoimmunity and cancers. A review is presented of the mechanisms by which a balance is maintained between infections caused by pathogens (viral, bacterial and protozoan; intracellular and extracellular) and disorders resulting from (acute or chronic) inflammation, and of the interactions that determine how the initial innate immune system directs subsequent acquired immune responses in human populations

NRAMP1 (SLC11A1): A Plausible Candidate Gene for Systemic Sclerosis (SSc) with Interstitial Lung Involvement

Systemic sclerosis (SSc), also termed "scleroderma," is a progressive, systemic disease of unknown origin characterized by excessive fibrosis, vascular abnormalities and immune dysfunction. Nramp 1 gene has multiple pleiotropic effects on macrophage activation pathways, including up-regulation of the chemokine/cytokine genes KC, tumor necrosis factor alpha, interleukin-1 b, inducible nitric oxide syntase, and major histocompatibility complex class II expression, as well as tumoricial activity and antimicrobial activity. All of these pleiotropic effects are important for resistance to infection, but they may also be involved in the induction and maintenance of autoimmune diseases. We analyzed four natural resistance associated macrophage protein 1 (NRAMP1) gene polymorphisms including 5' promoter (GT)n microsatellite, INT4 (469 + 14G/C), 3'UTR (1729 + 55del4), and D543N (codon 543, Asp to Asn) in 52 systemic sclerosis patients with interstitial lung involvement and 136 healthy controls. We found a significant association between INT4, (GT)n polymorphisms (p = 0.006 and 0.027, respectively), and SSc. Our findings suggest that NRAMP1 is a plausible candidate gene for SSc.

Relationship between Crohn’s disease, infection with Mycobacterium avium subspecies paratuberculosis and SLC11A1 gene polymorphisms in Sardinian patients

AIM: To study the association between Crohn’s disease (CD), Mycobacterium avium subspecies paratuberculosis (MAP), and genetic factors by examining the role of natural resistance-associated macrophage protein 1 (NRAMP1) gene polymorphisms (now SLC11A1) in Sardinian patients with CD and controls.

METHODS: Thirty-seven CD patients and 34 controls with no inflammatory bowel disease (IBD) were recruited at the University of Sassari after giving written consent. Six SCL11A1 polymorphisms previously reported to be the most significantly associated with IBD were searched. M. paratuberculosis was identified by IS900 PCR and sequencing. Logistic regression was used to calculate odds ratios (OR) for the associations among CD, presence of MAP, and 6 loci described above.

RESULTS: For the first time, a strong association was observed between polymorphisms at NRAMP1 locus 823C/T and CD. While CD was strongly associated with both NRAMP1 and MAP, NRAMP1 polymorphisms and MAP themselves were not correlated.

CONCLUSION: Combined with previous work on the NOD2/CARD15 gene, it is clear that the interplay of genetic, infectious, and immunologic factors in the etiology of CD is complex.

The -237C-->T promoter polymorphism of the SLC11A1 gene is associated with a protective effect in relation to inflammatory bowel disease in the South African population

The purpose of this study was to assess the likelihood that variation in the promoter region of the solute carrier family 11 member 1 gene (SLC11A1) contributes to inflammatory bowel disease (IBD) susceptibility in the South African population. The study cohort included 102 IBD patients, 47 with Crohn's disease (CD) and 55 with ulcerative colitis, and 192 population-matched controls. Mutation analysis revealed two novel alleles for the 5'-(GT)n repeat polymorphism, t(gt)5ac(gt)5ac(gt)6ggcaga(g)6 (allele 8) and t(gt)5ac(gt)5ac(gt)8ggcaga(g)6 (allele 9), and one previously documented point mutation -237C-->T. A significantly decreased frequency of the -237C-->T promoter polymorphism was observed in the patient group with IBD (p<0.001) and CD (p<0.0006) compared with the population-matched control group. These findings may be related to previous in vitro studies, which demonstrated that the point mutation at nucleotide position -237 represents a functional polymorphism that affects regulation of the upstream 5'-(GT)n repeat polymorphism differentially upon iron loading. Our findings raise the possibility that iron dysregulation mediated by allelic effects of SLC11A1 may contribute to IBD susceptibility.

Slc11a1 (formerly Nramp1) polymorphisms and susceptibility to post-transplant lymphoproliferative disease following pediatric liver transplantation

BACKGROUND

Polymorphisms of the solute carrier family 11 member 1 (Slc11a1) gene have previously been associated with susceptibility to infectious disease, anti-tumor defenses, and autoimmune diseases. We postulated that polymorphisms of the gene may also be associated with susceptibility to post-transplant lymphoproliferative disease (PTLD), a disease thought to be related to an impaired immune response to Epstein-Barr virus (EBV) in immunosuppressed patients.

METHODS

Whole blood samples were obtained from 45 pediatric patients who underwent liver transplantation. Polymerase chain reaction (PCR) was used to amplify a 3' region of the gene that includes an exon 15 single-nucleotide substitution (referred to as D543N) and a 4-bp deletion polymorphism (referred to as 3'-UTR). PCR products were digested using AvaII and FokI restriction enzymes for the D543N and 3'-UTR polymorphisms, respectively. PTLD disease status and EBV virus serum titers of all patients were obtained from hospital records.

RESULTS

Six of the 45 pediatric transplant recipients developed PTLD. An association was found between 3'-UTR polymorphisms of Slc11a1 and incidence of PTLD after liver transplantation (P = 0.005). In addition, post-transplant serum EBV titers were higher (P = 0.009) for recipients with certain Slc11a1 polymorphisms. No association was found between the D543N polymorphism and incidence of PTLD.

CONCLUSION

3'-UTR polymorphisms of the Slc11a1 gene appear to be associated with susceptibility to PTLD and the immune response to EBV in pediatric liver transplant recipients. Genotyping of pediatric patients undergoing liver transplantation may enable early identification of patients at high risk for developing high EBV titers and/or PTLD.

Global distribution of a novel trinucleotide microsatellite polymorphism (ATA)n in intron 8 of the SLC11A1 gene and susceptibility to pulmonary tuberculosis

We identified a novel trinucleotide (ATA)n repeat polymorphism in intron 8 of SLC11AI, a candidate gene for susceptibility to tuberculosis (TB) infection. We characterized the frequency of this polymorphism in 485 individuals originating from eight globally diverse human populations and compared the distribution of (ATA)n alleles in 146 adults and in 80 cord blood samples from newborns in the Gambian population. Lastly, we tested for association of this microsatellite with pulmonary TB in 318 TB cases and 146 controls in the Gambian population. We found no significant difference in frequency or distribution of alleles in adult and cord blood samples, and we found no significant association between this marker and pulmonary TB.

NRAMP1 is not associated with asthma, atopy, and serum immunoglobulin E levels in the French Canadian population

Reduced infection by mycobacteria, including Mycobacterium tuberculosis, may be partly responsible for increased prevalence of allergic and autoimmune diseases in developed countries. In a murine model of innate resistance to mycobacteria, the Nramp1 gene has been shown to affect asthma susceptibility. From this observation, it was proposed that human NRAMP1 may be a modulator of asthma risk in human populations. To experimentally test the candidacy of NRAMP1 in asthma susceptibility, we characterized five genetic variants of NRAMP1 (5'CAn, 274C>T, 469+14G>C, D543N, and 1729+del4) in an asthma family-based cohort from northeastern Quebec. We did not observe any significant association between NRAMP1 variants (either allele or haplotype specific) with asthma, atopy, or serum immunoglobulin E levels. These results demonstrate that, in spite of direct involvement of Nramp1 in a murine asthma model, in human populations NRAMP1 is not likely to be a major contributor to the genetic etiology of asthma and asthma-related phenotypes.

NRAMP1 gene polymorphism and susceptibility to nontuberculous mycobacterial lung diseases

STUDY OBJECTIVES

Pulmonary disease caused by nontuberculous mycobacteria (NTM) may occur in patients with no underlying lung disease and no known immunodeficiency. The purpose of this study was to evaluate a potential role for natural-resistance-associated macrophage protein 1 (NRAMP1) gene polymorphisms for human susceptibility to the NTM lung disease.

DESIGN

A case-control study.

SETTING

Tertiary university medical center.

PARTICIPANTS

Forty-one adult patients with NTM lung disease (Mycobacterium avium complex infection, 18 patients; Mycobacterium abscessus infection, 23 patients) were included in the study population. The diagnosis of NTM lung disease was made when the patients fulfilled the diagnostic criteria published by the American Thoracic Society. All patients had findings on high-resolution CT scans, such as bilateral bronchiectasis combined with multiple small nodules and branching linear structures, that were characteristic of the nodular bronchiectatic form of NTM lung disease. Fifty healthy individuals were selected as control subjects.

RESULTS

Heterozygotes at intron 4 (469 + 14G/C) [INT4], codon 543 in exon 15 (D543N), and 3' untranslated region (3'UTR) were observed at significantly higher frequencies in patients with NTM lung disease than in control subjects. The odds ratios (ORs) were 2.78 (95% confidence interval [CI], 1.12 to 6.89; p = 0.026) for INT4 G/C, 5.74 (95% CI, 1.48 to 22.30; p = 0.006) for D543 G/A, and 9.54 (95% CI, 2.49 to 36.53; p < 0.001) for 3'UTR TGTG+/del. Subjects who were heterozygous for two NRAMP1 polymorphisms in INT4 and D543N were particularly overrepresented among those with NTM lung disease, compared with those with the most common NRAMP1 genotype (OR, 10.88, 95% CI, 1.18 to 100.45; p = 0.035). There were no significant differences in the frequencies of INT4, D543N, and 3'UTR polymorphisms between the patients with M avium complex infection and those with M abscessus infection.

CONCLUSIONS

These findings suggest that the NRAMP1 genetic polymorphisms are associated with human susceptibility to NTM lung disease.

Promoter polymorphism of SLC11A1 (formerly NRAMP1) confers susceptibility to autoimmune type 1 diabetes mellitus in Japanese

Defective function of antigen-presenting cells has been postulated to be one of the non-HLA-linked susceptibility factors for type 1 diabetes mellitus, though the underlying genetic factors remain unclear. SLC11A1 (formerly NRAMP1), a divalent cation transporter, plays a crucial role in macrophage activation. We performed a case-control study in 224 healthy and 95 type 1 diabetic Japanese subjects, examining the length polymorphisms in the promoter region (-377 to -222) of SLC11A1, which may influence transcriptional activity. Alleles designated 2, 3, and 7 have been identified in Japanese subjects. The frequency of allele 7 was significantly higher in subjects with type 1 diabetes (9.47%) than in the healthy controls (4.46%). The difference is more marked in the subpopulation of Japanese subjects with type 1 diabetes; diabetic subjects with at least one protective HLA class II allele and those without any susceptibility HLA class II haplotypes, DR4-DQ4 or DR9-DQ9, had a much higher allele 7 frequency than controls. These findings suggest that the novel promoter polymorphism of SLC11A1 influences the susceptibility to type 1 diabetes in Japanese subjects.

Expression of the SLC11A1 (NRAMP1) 5′-(GT)n repeat: Opposite effect in the presence of −237C→T

Association of various autoimmune and infectious diseases with genetic variation in the solute carrier family 11 member 1 (SLC11A1) gene, formerly known as the natural resistance-associated macrophage protein 1 (NRAMP1) gene, is in accordance with its role in iron metabolism and immune function. In this investigation, in vitro studies were performed to determine whether allelic variants in the promoter region of the gene are affected by iron loading, thereby leading to differential expression of SLC11A1. Constructs containing five different SLC11A1 5'-(GT)n polymorphic alleles identified in the South African population (alleles 2, 3, 5, 8, and 9) and a C to T point mutation at nucleotide position -237, both in the absence and presence of allele 3, were cloned into the pGL2-Basic luciferase-reporter vector and transfected into U937 and THP-1 cells. Addition of exogenous stimuli, including interferon-gamma, bacterial lipopolysaccharide, and ferric ammonium citrate, demonstrated significant differences in the ability of these alleles to regulate gene expression. Striking differences were obtained upon iron loading, with allele 3 showing opposite effects in the presence or absence of promoter polymorphism -237C-->T. Our findings provide direct evidence that this promoter polymorphism is functional and support the hypothesis that iron dysregulation mediated by allelic effects of SLC11A1 underlies disease susceptibility linked to infectious and autoimmune conditions.

SLC11A1 (formerly NRAMP1) and susceptibility to visceral leishmaniasis in The Sudan

Genetic susceptibility to visceral leishmaniasis (VL) is indicated by differences in incidence and clinical phenotypes between ethnic groups in Sudan. In mice, innate susceptibility to Leishmania donovani, the etiological agent of VL, is controlled by Slc11a1 (formerly Nramp1). We therefore examined polymorphisms at SLC11A1 in 59 multicase families of VL from the high-incidence Masalit tribe in Sudan. Multipoint nonparametric analysis in ALLEGRO shows a significant linkage across SLC11A1 (Zlr scores 2.38-2.55; 0.008< or =P< or =0.012; information content 0.88). The extended transmission disequilibrium test shows biased transmission of alleles at 5' polymorphisms in the promoter (P=0.0145), exon 3 (P=0.0037) and intron 4 (P=0.0049), and haplotypes formed by them (P=0.0089), but not for 3' polymorphisms at exon 15 or the 3'UTR. Stepwise logistic regression analysis using a case/pseudo-control data set derived from the 59 families was consistent with main effects contributed by the intron 4 469+14G/C polymorphism. Although the two alleles for 469+14G/C lie on haplotypes carrying different alleles for the functional promoter GTn polymorphism, the latter did not itself contribute separate main effects. Sequence analysis of 36 individuals failed to identify new putative functional polymorphisms in the coding region, intron 1, intron/exon boundaries, intron 4/exon 4a, or in the 3'UTR. One novel promoter polymorphism (-86G/A) was located within a putative nuclear factor kappa B binding site that could be functional. Further work will determine whether additional polymorphisms occur upstream in the promoter, which could be in linkage disequilibrium with the intron 4 polymorphism. These studies contribute to knowledge of the role of SLC11A1 in infectious disease.

Is rheumatoid arthritis a consequence of natural selection for enhanced tuberculosis resistance?

Although the bubonic plague or "Black Death" is notorious for the toll it took on the population of Europe in the middle ages, another epidemic, the "White Death" of tuberculosis is responsible for millions of deaths worldwide over the past 300 years. With one in four deaths due to tuberculosis in Western Europe and the United States in the 19th century, this disease undoubtedly acted as a powerful genetic selective force. The epidemiology of modern day rheumatoid arthritis (RA) is strikingly similar to the epidemiology of tuberculosis 100-200 years ago, suggesting the possibility that genetic factors that enhanced survival in tuberculosis epidemics are now influencing susceptibility to RA. Recent advances in the analysis of genetic polymorphisms associated with disease have identified several genes linked to RA susceptibility that encode proteins involved in the immune response to Mycobacterium tuberculosis infection, including TNF-alpha, NRAMP1, PARP-1, HLA-DRB1, and PADI4. These results suggest that rheumatoid arthritis, and possibly other autoimmune diseases, are modern day manifestations of the genetic selective pressure exerted by tuberculosis epidemics of the recent past.

Comparative analysis of two slc11 (Nramp) loci in Takifugu rubripes

To study the evolution of the solute carrier family 11 (slc11; formerly Nramp) protein, we isolated and characterized two paralogs from the pufferfish Takifugu rubripes (Fugu). These teleost genes, designated Fugu slc11a-a and Fugu slc11a-b, comprise open reading frames of 1743 nucleotides (581 amino acids) and 1662 nt (554 aa), respectively. The proteins are 81% similar, and both exhibit signature features of the slc11 family of proteins including 12 transmembrane domains, a conserved transport motif and a glycosylated loop. Both Fugu paralogs are more Slc11a2-like based on sequence homology and phylogenetic studies. Analysis of gene environment placed both in the proximity of multiple loci syntenic to human chromosome 12q13, that is, within a SLC11A2 gene environment. However, Fugu slc11a-a also gave one match with chromosome 2q35, where human SLC11A1 resides. Functional diversification was suggested by differences in tissue distribution and subcellular localization. Fugu slc11a-a exhibits a restricted expression profile and a complex subcellular localization, including LAMP1 positive late endosomes/lysosomes in transiently transfected mouse macrophages. Fugu slc11a-b is expressed ubiquitously and localizes solely to late endosomes/lysosomes. This comparative analysis extends our understanding of the evolution and function of this important family of divalent cation transporters. [Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession nos. AJ496547/8/9 and AJ496550.]

The Role of Iron in the Pathogenesis of Experimental Allergic Encephalomyelitis and Multiple Sclerosis

Multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), are autoimmune disorders resulting in demyelination in the central nervous system (CNS). Pathologically, the blood-brain barrier becomes damaged, macrophages and T cells enter into the CNS, oligodendrocytes and myelin are destroyed, astrocytes and microglia undergo gliosis, and axons become transected. Data from several biochemical and pharmacological studies indicate that free radicals participate in the pathogenesis of EAE, and iron has been implicated as the catalyst leading to their formation. The primary focus of this article is the examination of the role of iron in the pathogenesis of MS and EAE. Particular attention will be paid to the role and distribution of iron and proteins involved with iron metabolism (e.g., transferrin, ferritin, heme oxygenase-1, etc.) in normal and disease states of myelin. Furthermore, therapeutic interventions aimed at iron, iron-binding proteins, and substrates or products of iron-catalyzed reactions leading to free radical production will be discussed.

Extent and distribution of linkage disequilibrium around the SLC11A1 locus

The SLC11A1 (or NRAMP1) locus on human chromosome 2q35 encodes for the protein solute carrier family 11, member 1. It is expressed in macrophages and involved in the early stages of macrophage priming and activation. Different association studies have shown that the SLC11A1 gene affects susceptibility to infectious diseases and autoimmune inflammatory diseases. Although functional SLC11A1 polymorphisms may account for its role in affecting the susceptibility to these diseases, the positive association can also be because of flanking polymorphisms showing linkage disequilibrium (LD) with this locus. This is the first systematic study to investigate the LD pattern within and around the gene. LD was investigated by genotyping 17 genetic markers in a Chinese population (n=360). The results indicate that LD is maintained at least 110 kb both upstream and downstream of the locus. The complex LD pattern demands that association studies with SLC11A1 should be carried out with both 5' and 3' markers. The strong LD between IL8RB and the 5' SLC11A1 markers also dictates that IL8RB be tested for association with these diseases. Thus, positive association with SLC11A1 should be interpreted cautiously, and IL8RB should also be considered as a potential candidate susceptibility gene unless proven otherwise.

Atopy in children in relation to BCG vaccination and genetic polymorphisms at SLC11A1 (formerly NRAMP1) and D2S1471

The influence of the SLC11A1 (formerly NRAMP1) gene on the association between BCG vaccination and atopy in children was studied in 179 children, BCG vaccinated in infancy, and 307 children without BCG vaccination, all 3 to 8 years of age and with atopic heredity. DNAs were genotyped for a functional repeat polymorphism (designated GTn) in the promoter of SLC11A1 and a linked microsatellite D2S1471. Associations between genotype, atopic symptoms and allergen-specific IgE-antibodies in relation to the BCG status of the children were assessed. Atopy in relation to SLC11A1 GTn-alleles was similarly distributed between the two groups. In BCG vaccinated children, genotype associations were observed for D2S1471 and atopy, with carriage of allele 5 conferring increased risk of atopy (odds ratio (OR) 2.6; 95% confidence interval (CI) 1.3-5.5; P = 0.01), and particularly IgE responses to airborne allergens (OR = 4.3; 95% CI 1.7-10.7; P = 0.002). No linkage disequilibrium was found between the SLC11A1 GTn repeat and the microsatellite D2S1471, and therefore no haplotype associations were observed for atopy in BCG- or non-BCG vaccinated children. Stratification by BCG vaccination unmasked a potential genetic risk factor for atopy in the region of the SLC11A1 locus, and point to the importance of genotype by environment interactions in determining disease susceptibility.